Fluorescein-labeled glutathione to study protein S-glutathionylation.

Numerous studies of S-glutathionylation of cysteine thiols indicate that this protein modification plays a key role in redox regulation of proteins. To facilitate the study of protein S-glutathionylation, we developed a synthesis and purification to produce milligram quantities of fluorescein-labeled glutathione. The amino terminus of the glutathione tripeptide reacted with fluorescein isothiocyanate readily in ammonium bicarbonate.